As it becomes clear that 21st century will be a silver society, people pursuit for high quality in life by having healthy and longer life without harmful diseases. Development in science increased the number of aged people to have longer life, and consequently it led to sudden increase rate in patients with Alzheimer's disease, which caused from neurological degeneration. Alzheimer's disease not only deteriorates the quality of personal and social life, but also puts the patients themselves and others in misery. Alzheimer's disease is the fourth highest death reason followed by cancer, heart disease, and cerebral apoplexy.
Studied statistics of the advanced countries show the percentage in number of patients with Alzheimer's disease increase with increase in age: 60s 15-20%, 70s 30-40%, and 80s 60%. That is, the situation becomes serious in 80s that one in every couple is to have Alzheimer's disease. There is no accurate statistical data in Korea yet; however knowing more than 12 million people suffer from the disease in Japan, the United States, and Europe, we can predict the numbers to grow fast in close future.
There are several reasons in the causes of Alzheimer's disease. First, the Alzheimer's disease is caused by the lowering concentration of neurotransmitter, acetylcholine. Acetylcholine having a quaternary amine structure is a neurotransmitter that, with acetylcholinesterase, is hydrolyzed to choline. According to the prior researches, the patients with Alzheimer's disease have low concentration of acetylcholine, and when acetylcholinesterase is inhibited, its concentration increases to improve the symptoms of Alzheimer's disease. Current medicinal substances used for treating Alzheimer's disease are synthetic acetylcholinesterase inhibitors such as Tarcrine (1) and Donepezil (2), illustrated in Formula 1. Another substance currently on clinical examination is Huperzine A, which is also an acetylcholinesterase inhibitor obtained from Hupersia Serrata.

Second, the Alzheimer's disease can be delayed in its progression by studying genetic factors of Alzheimer's disease that relate to β-amyloid synthesis, progression, accumulation of neuron, and β-amyloid settlement in the cortex. Likewise, by finding control actors for lowering β-amyloid concentration outside the cell and selectively removing β-amyloid settlement inside the brain, the Alzheimer's disease can be treated. β-amyloid aggregation is a substantial cause of Alzheimer's disease, thus active researches are done on the matter to suppress its forming.
Third, the Alzheimer's disease can be treated by using estrogen, an antioxidants, a free radical scavengers or anti-inflammatory agents. As a result, the disease progress can be prevented indirectly.
Fourth, the Alzheimer's disease can be treated by preventing gradual and irreversible degeneration of the synapse and neurons.
Currently, the therapeutics for Alzheimer's disease that have been approved by Food and Drug Administration (FDA) in the U.S. are all acetylcholinesterase inhibitors.
Among the therapeutics mentioned above, Tarcrine has side effects such as hepatotoxicity, abdominal spasm, vomiting, and diarrhea; moreover, it is efficacious to only about 25% of the patients with Alzheimer's disease. Meanwhile, Donepezil is more selective to acetylcholine, and has fewer side effects compared to Tarcrine; however, it is much less effective in treating the disease.